Semiconductor devices are commonly found in modern electronic products. Semiconductor devices vary in the number and density of electrical components. Discrete semiconductor devices generally contain one type of electrical component, e.g., light emitting diode (LED), small signal transistor, resistor, capacitor, inductor, and power metal oxide semiconductor field effect transistor (MOSFET). Integrated semiconductor devices typically contain hundreds to millions of electrical components. Examples of integrated semiconductor devices include microcontrollers, microprocessors, charged-coupled devices (CCDs), solar cells, and digital micro-mirror devices (DMDs).
Semiconductor devices perform a wide range of functions such as signal processing, high-speed calculations, transmitting and receiving electromagnetic signals, controlling electronic devices, transforming sunlight to electricity, and creating visual projections for television displays. Semiconductor devices are found in the fields of entertainment, communications, power conversion, networks, computers, and consumer products. Semiconductor devices are also found in military applications, aviation, automotive, industrial controllers, and office equipment.
Semiconductor devices exploit the electrical properties of semiconductor materials. The atomic structure of semiconductor material allows its electrical conductivity to be manipulated by the application of an electric field or base current or through the process of doping. Doping introduces impurities into the semiconductor material to manipulate and control the conductivity of the semiconductor device.
A semiconductor device contains active and passive electrical structures. Active structures, including bipolar and field effect transistors, control the flow of electrical current. By varying levels of doping and application of an electric field or base current, the transistor either promotes or restricts the flow of electrical current. Passive structures, including resistors, capacitors, and inductors, create a relationship between voltage and current necessary to perform a variety of electrical functions. The passive and active structures are electrically connected to form circuits, which enable the semiconductor device to perform high-speed calculations and other useful functions.
Semiconductor devices are generally manufactured using two complex manufacturing processes, i.e., front-end manufacturing, and back-end manufacturing, each involving potentially hundreds of steps. Front-end manufacturing involves the formation of a plurality of die on the surface of a semiconductor wafer. Each semiconductor die is typically identical and contains circuits formed by electrically connecting active and passive components. Back-end manufacturing involves singulating individual semiconductor die from the finished wafer and packaging the die to provide structural support and environmental isolation.
The terms “die”, “semiconductor chip”, and “semiconductor die” are used interchangeably throughout this specification. The term wafer is used herein include any structure having an exposed surface onto which a layer is deposited according to the present invention, for example, to form the circuit structure.
FIGS. 1A through 1E show schematic, cross-sectional diagrams of a typical method for fabricating a semiconductor package having a redistribution layer (RDL).
Referring to FIG. 1A, multiple semiconductor dies 100 are placed onto an adhesive layer 102, which in turn is applied to a carrier substrate 104. Each die 100 includes a substrate made of a semiconductor material, such as gallium arsenide (GaAs), gallium nitride (GaN), or silicon (Si) with an integrated circuit formed thereon (or therein). Next, as illustrated in FIG. 1B, an encapsulation material 106 is deposited (or formed) over the semiconductor die 100 and on the exposed portions of the adhesive layer 102. Depending on the material used as the encapsulation material 106, a curing process is then performed to at least partially cure the encapsulation material 106.
After the encapsulation material 106 is cured, the encapsulation material 106 becomes partially rigid and forms an encapsulated structure. The encapsulated material 106 has an initial thickness that is greater than desired. Thus, an exposed surface of the encapsulation material 106 undergoes a grinding (and/or polishing and/or abrasion) process to expose the die 100 as shown in FIG. 1C. In some instance, the surface of the encapsulation material 106 may be subjected to a chemical mechanical polishing process. Referring to FIG. 1D, an RDL layer 108 is formed over the die 100, including various insulating layers and conductive traces in electrical communication with the die 100. Also, contact formations (e.g., solder balls) 110 can be formed in electrical communication with the RDL layer 108. Referring to FIG. 1E, the carrier substrate 104 and adhesive layer 102 are then de-bonded from the structure. From here, the structure can be cut or diced into individual semiconductor devices having respective ones of the die 100.
Packaging processes such as the one described above have several drawbacks. The encapsulation process typically includes the use of the carrier substrate 104 because strong mechanical support is desired to prevent warping. The addition and removal of the carrier substrate 104 add additional steps to the process that increase time and expense of manufacturing. Also, additional encapsulant is used to fill the gaps between die 100. This also adds to manufacturing expense and increases manufacturing time because of the step of grinding away excess encapsulant. Thus, there exists a desire in the industry for improved packaging processes that can reduce cost and manufacturing time compared to such prior processes.